A 9-month-long continuous flow column study was carried out to investigate Cr(VI) removal by Fe0 with the presence of humic acid. The study focused on the influences of humic acid promoted dissolved iron release and humic acid aggregation in Fe0 columns receiving synthetic Cr(VI) contaminated groundwater containing various components such as bicarbonate and Ca. The effects of humic acid varied significantly depending on the presence of Ca. In Ca-free columns, the presence of humic acid promoted the release of dissolved iron in the forms of soluble Fe-humic acid complexes and stabilized fine Fe (hydr)oxide colloids. As a result, the precipitation of iron corrosion products was suppressed and the accumulation of secondary minerals on Fe0 surfaces was diminished, and a slight increase in Cr(VI) removal capacity by 18% was record compared with that of humic acid-free column. In contrast, in the presence of Ca, as evidenced by the SEM and FTIR results, humic acid greatly co-aggregated with Fe (hydr)oxides and deposited on Fe0 surfaces. This largely inhibited electron transfer from Fe0 surfaces to Cr(VI) and reduced the drainable porosity of the Fe0 matrix, resulting in a significant decrease in Cr(VI) removal capacity of Fe0. The Cr(VI) removal capacity was decreased by 24.4% and 42.7% in humic acid and Ca receiving columns, with and without bicarbonate respectively, compared with that of Ca and humic acid-free column. This study yields new considerations for the performance prediction and design of Fe0 PRBs in the environments rich in natural organic matter (NOM).

Petroleum monoaromatics including benzene, toluene, ethylbenzene, and xylenes (BTEX) are among the notorious volatile organic compounds that contaminate water and soil. In this study, a surfactant- modified natural zeolite and its relevant granulated nanozeolites were evaluated as potential adsorbents for removal of petroleum monoaromatics from aqueous solutions. All experiments performed in batch mode at constant temperature of 20°C and pH of 6.8 for 48 h. The results revealed that the amount of BTEX uptake on granulated zeolites nanoparticles were remarkably higher than the parent micron size natural zeolite (in the order of four times). The isotherms data were analyzed using five models namely, Langmuir, Fruendlich, Elovich, Temkin, and Dubinin–Radushkevich models. It was concluded that the Langmuir model fits the experimental data. The measured adsorption capacities were 3.89 and 4.08 mg of monoaromatics per gram of hexadecyltrimethylammonium-chloride and n-cetylpyridinium bromide (CPB)-modified granulated nanozeolite, respectively. Considering the type of surfactant, adsorbents modified with CPB showed greater tendency for the adsorption of the adsorbates.

In this study, a fast bioassay using the ECOTOX system to evaluate biological safety of waste water samples from different sources was performed. This biological system works full automatically to test water quality. The system uses the image analysis of movement behavior of the flagellate Euglena gracilis as a model organism. The measured parameters are cell motility, velocity, orientation (r-value, upward swimming and alignment) as well as cell form (compactness). In most tested waste samples, precision of orientation (r-value) is inhibited at concentrations which showed less effect on the other parameters. Motility and compactness were noticed to be the least inhibited parameters in response to waste water samples. The results of waste treatment plants revealed the efficiency of the used purification system. Movement as well as orientation parameters in E. gracilis showed high sensitivity toward chlorine. The order of sensitivity was motility > velocity > r-value > upward swimming with EC50 values of 0.69, 0.81, 0.85, and 1.78 mg L−1, respectively. ECOTOX with its test organism (E. gracilis) provides an automatic, fast and sensitive system to monitor water samples.

The present investigation was carried out to evaluate the detoxification potential of Pseudomonas fluorescens SM1 strain immobilized in calcium alginate beads for some major toxicants of Indian water bodies. The toxicants selected in this study were benzene hexachloride, mancozeb, 2,4-dichloro-phenoxyacetic acid (pesticides); phenol, catechol, cresol (phenolics); and Cd++, Cr(VI), Cu++ and Ni++ (heavy metals), which were taken as mixtures up to a concentration of roughly twice that usually found in highly polluted sites. Allium cepa phytotoxicity test, Ames fluctuation test and plasmid nicking assay were employed to estimate the phytotoxicity and genotoxicity of the model water containing the test toxicants under different combinations before and after exposure to our bioremediation-cum-detoxification system. The IC50 of the model water containing all the test toxicants, treated with the immobilized SM1 cells, was recorded to be 0.7× compared to 0.06× for the same but untreated water sample, enhancing the IC50 value by 12-fold. The IC25 of the test heavy metal mixture only could enhance from 0.07 to 1.30× (18-fold). The IC25 of the test pesticide mixture alone was increased from 0.07 to 1.71× (24-fold). The IC25 values for the mixture of test phenolics were 0.07× and 2.18× under the pre- and post-treatment conditions, respectively, exhibiting a 31-fold increase. A mutational induction (Mi) corresponding to the 0.5 value in the Ames fluctuation test was used to evaluate the mutagenicity of the test model water containing all the toxicants before and after exposure to the immobilized SM1 cell system. The Mi (0.5) value with the TA98 tester strain was estimated to be 0.08× for the untreated and 0.6× for the treated model water, whereas the same index was calculated to be 0.48× and 1.8×, respectively, for the TA100 strain. A remarkable improvement in the quality of the test water as a result of exposure to this bioremediating system was observed in terms of the absence of the linear form of the plasmid contrary to the visible linearization with the untreated model water. In view of the above findings, it is quite clear that the test of P. fluorescens SM1 strain immobilized in the calcium alginate beads could be used as an efficient system of bioremediation and for water decontamination strategies owing to its remarkable detoxification potential.

Cr3+ sorption on strong acid exchanger Amberlyst-15(H+) is studied as a function of time and temperature using CrCl3.6H2O and [Cr4(SO4)5(OH)2] solutions. The rate is found to be governed by a mixed diffusion for both the solutions and faster for Cl1− solution than SO4 2−. The exchange capacities are found to be higher for Cl1− system than SO4 2−. From the rate constant values, the energies of activation are calculated using the well-known Arrhenius equation. Equilibrium data is explained with the help of the Langmuir equation. The Langmuir parameters are also found to be higher for exchange from the chloride solutions. Various thermodynamic parameters (ΔHo, ΔSo, and ΔGo) for Cr3+ exchange on the resin are calculated. The ΔGo values are found to be negative while ΔHo and ΔSo are positive for both the Cr3+/Cl1− and Cr3+/SO4 2− systems. It is suggested that in case of Cl1− solutions, the metal is exchanged as Cr3+, while in case of SO4 2− solutions, the metal exchanging specie is CrSO4 +.

Concrete grinding residue (CGR) is a by-product created by concrete pavement maintenance operations. The application of CGR to roadside soils is not consistently regulated by state agencies across the USA, which is partially due to the lack of science-based information on its impacts to soils and plants. The objectives of this research were to determine the impact of CGR additions to soil on both smooth brome (Bromus inermis L.) biomass and plant and soil chemical parameters. In a greenhouse study, two soils were treated with two CGR by-products at 8% and 25% by weight. Shoot biomass was significantly influenced by the main effects (Soil, CGR, and Rate) and by all two-way interactions, but not consistently positively or negatively correlated. Trace metal concentrations in the shoot biomass were variable, but 68% of these metals had the same concentration or lower in the 25% CGR treatments compared with the controls. Soil pH and electrical conductivity were significantly influenced by the main effects and two-way interactions of Soil × Rate and CGR × Rate, and soil pH was significantly greater in the CGR-treated soils. Calcium, Na, Mg, Al, and S concentrations in soils were all influenced by additions of CGR, but trace metal levels in the treatments were all within the range for uncontaminated soils. Ecosystem impact of applying CGR will be dependent upon the quality of CGR and soil characteristics. Controlling the liming potential of CGR should be considered a best management practice.

The detailed characterization of the organic composition of industrial effluents discharged from various industrial branches and the distribution of the emitted pollutants in the surface waters in North Rhine-Westphalia have been done with the use of non-target screening analyses. Based on the characterization of molecular structures of wastewater constituents, their quantification as well as the available information on their origin and industrial applications, the identification of typical organic representatives for petrochemical and food effluents has been performed. Among a wide range of hydrocarbons detected in the petrochemical effluents, several novel organic wastewater constituents have been found for the first time. In the effluents from paper production plant, potential industrial indicators were distinguished, such as resin acids (abietic and dehydroabietic acids) and photoinitiators (Irgacure 184). The monitoring of the behaviour of certain environmentally relevant and newly described pollutants in the contaminated river systems allowed the identification of several industrial site-specific markers. Particularly, 2-(chloromethyl)-1,3-dioxolane, an unknown contaminant, exclusively found in the effluents from a chemical production complex, was present in the river under discharge at high concentrations downstream the contamination source. The comprehensive and detailed evaluation of the anthropogenic markers in the industrial effluents is a promising tool for the environmental assessment of industrial emissions, especially if accompanied with toxicological and ecotoxicological investigations of novel environmental contaminants.

Granular bentonite has been assessed regarding its capacity to remove Hg(II), Cd(II) and Pb(II) from aqueous solutions. Sorption capacities, kinetics and the dependence of the sorption process on pH were determined. Fractional power, pseudo-first-order, pseudo-second-order and intra-particle diffusion equations were used to model the kinetics of metal adsorption. The pseudo-second-order model showed the best fit to experimental data. Different two-parameter sorption isotherm models (Langmuir, Freundlich, Temkin and Dubinin–Radushkevich) were used to fit the equilibrium data. Freundlich's isotherm model gave the best fit to experimental data. The selectivity of granular bentonite towards these metals is Pb(II) > Cd(II) > Hg(II). The adsorption capacities of granular bentonite towards the metals expressed in milligramme metal per gramme granular bentonite are 19.45, 13.05 and 1.7 for Pb(II), Cd(II) and Hg(II), respectively (for an initial concentration of 100 mg metal/L).

Karst watersheds are a major source of drinking water in the European Alps. These watersheds exhibit quick response times and low residence times, which might make karst aquifers more vulnerable to elevated nitrogen (N) deposition than non-karst watersheds. We summarize 13 years of monitoring NO3 −, NH4 +, and total N in two forest ecosystems, a Norway spruce (Picea abies (L.) Karst.) forest on Cambisols/Stagnosols (IP I) and a mixed beech (Fagus sylvatica L.) spruce forest on Leptosols (IP II). N fluxes are calculated by multiplying concentrations, measured in biweekly intervals, with hydrological fluxes predicted from a hydrological model. The total N deposition in the throughfall amounts to 26.8 and 21.1 kg/ha/year in IP I and IP II, respectively, which is high compared to depositions found in other European forest ecosystems. While the shallow Leptosols at IP II accumulated on average 9.2 kg/ha/year of N between 1999 and 2006, the N budgets of the Cambisols/Stagnosols at IP I were equaled over the study period but show high inter-annual variation. Between 1999 and 2006, on average, 9 kg/ha/year of DON and 20 kg/ha/year of DIN were output with seepage water of IP I but only 4.5 kg/ha/year of DON and 7.7 kg/ha/year of DIN at IP II. Despite high DIN leaching, neither IP I nor IP II showed further signs of N saturation in their organic layer C/N ratios, N mineralization, or leaf N content. The N budget over all years was dominated by a few extreme output events. Nitrate leaching rates at both forest ecosystems correlated the most with years of above average snow accumulation (but only for IP I this correlation is statistically significant). Both snow melt and total annual precipitation were most important drivers of DON leaching. IP I and IP II showed comparable temporal patterns of both concentrations and flux rates but exhibited differences in magnitudes: DON, NO3 −, and NH4 + inputs peak in spring, NH4 + showed an additional peak in autumn; the bulk of the annual NO3 − and DON output occurred in spring; DON, NO3 −, and NH4 + output rates during winter months were low. The high DIN leaching at IP I was related to snow cover effects on N mineralization and soil hydrology. From the year 2004 onwards, disproportional NO3 − leaching occurred at both plots. This was possibly caused by the exceptionally dry year 2003 and a small-scale bark beetle infestation (at IP I), in addition to snow cover effects. This study shows that both forest ecosystems at Zöbelboden are still N limited. N leaching pulses, particularly during spring, dictate not only annual but also the long-term N budgets. The overall magnitude of N leaching to the karst aquifer differs substantially between forest and soil types, which are found in close proximity in the karstified areas of the Northern Limestone Alps in Austria.

The heterogeneous photocatalytic water purification process has gained wide attention due to its effectiveness in degrading and mineralizing the recalcitrant organic compounds as well as the possibility of utilizing the solar UV and visible light spectrum. This paper aims to review and summarize the recently published works in the field of photocatalytic oxidation of toxic organic compounds such as phenols and dyes, predominant in wastewater effluent. In this review, the effects of various operating parameters on the photocatalytic degradation of phenols and dyes are presented. Recent findings suggested that different parameters, such as type of photocatalyst and composition, light intensity, initial substrate concentration, amount of catalyst, pH of the reaction medium, ionic components in water, solvent types, oxidizing agents/electron acceptors, mode of catalyst application, and calcinations temperature can play an important role on the photocatalytic degradation of organic compounds in water environment. Extensive research has focused on the enhancement of photocatalysis by modification of TiO2 employing metal, non-metal, and ion doping. Recent advances in TiO2 photocatalysis for the degradation of various phenols and dyes are also highlighted in this review.